The likelihood that only a handful of incumbents from either side will lose may in the end give the winning party a pickup as small as a single seat.

Because redistricting has given the parties — primarily Republicans — lopsided control of many districts and a working majority in many others, this is one of the narrowest fields of competitive races in recent memory. Twenty-six Democratic seats and 23 Republican seats are currently considered less than safe, according to ratings compiled by the Rothenberg Political Report and used by CQ Weekly and Roll Call. Of those, only 14 are regarded as highly competitive. (View ratings map.)

What’s more, this election is the first in at least a decade without a presidential race and also with no sign of an overriding issue such as the health care debate that helped Republicans win the House in 2010.

Region by region, and in some cases, state by state, Democrats and Republicans are battening down to protect the seats they have, while at the same time launching aggressive campaigns to pick off seats held by the opposition.

Democrats, who have a 17-seat deficit in the House, have the more difficult mission. After a somewhat shy start, party operatives have lately begun exploring challenges to GOP incumbents in normally safe Republican districts. They are stepping up the assertion that they can win back control of the House in 2014.

“We think there are enough competitive Republican-held districts out there to put the House in play,” says Kelly Ward, executive director of the Democratic Congressional Campaign Committee.

Likewise, a chief goal for Greg Walden, chairman of the National Republican Congressional Committee, is to bring down seven conservative Democrats who represent districts carried by the last three GOP presidential nominees.

“I call them ‘ The Slippery Seven,’ ” Walden said in July. “It’s not an ethical charge. They just keep getting away.”

Following is the House state of play, a little more than a year out from Election Day:

Mid-Atlantic

New York currently features more competitive races — seven — than any other state. All of these seats favor one party over the other, but both House campaign committees are paying close attention to the Empire State.

Upstate Republicans Tom Reed and Chris Gibson, along with Staten Island’s Michael G. Grimm, the only Republican who represents New York City, are three of the most endangered incumbents. But given the right candidates and circumstances, the GOP could pick off Democrats such as six-term veteran Timothy H. Bishop of Long Island and freshman Sean Patrick Maloney, who represents a stretch of the Hudson Valley.

Pennsylvania, which was a focal point in the 2006, 2008 and 2010 swing elections, has only two seats not rated completely safe.

Republican incumbent Michael G. Fitzpatrick is the most vulnerable. One national Democratic operative said that his district in the Bucks County suburbs of Philadelphia could generate an angry moderate backlash against the GOP. At the same time, though, Fitzpatrick proved to be a solid fundraiser this year, raising over a half-million dollars in the second quarter alone.

Then there is West Virginia.

After a quiet 2012, the Mountain State is the source of renewed political excitement. It’s in the middle of a transition from New Deal Democratic bastion to Republican stronghold. While registered Democrats heavily outnumber Republicans, the state hasn’t voted for a Democratic presidential nominee since 1996.

Republicans persuaded a Democratic state legislator, Evan Jenkins, to switch parties to challenge Democratic incumbent Nick J. Rahall II — Jenkins actually had been a registered Republican until he ran for state office in 1993.

But the Democrats are on offense as well. They are making noise about the opportunity presented by the open-seat race in the 2nd District to replace Republican Shelley Moore Capito, who is running for the Senate.

Midwest/Plains

Ohio, like neighboring Pennsylvania, is no longer the battleground it once was. The state used to be ground zero for competitive House races, but redrawn district lines mean Ohio may have just three competitive races out of 16 seats. Michigan’s number of competitive races also has declined to the current two from three in 2010.

Instead, Illinois is where the action is for this region in 2014.

While Illinois seats are now tougher for Republicans to pick up, thanks to redistricting led by Democrats, the lower turnout in a non-presidential-election year could create opportunities for the GOP.

Two former Republican House members, Robert Dold and Bobby Schilling, are readying rematches against their 2012 rivals. Both are running in districts that lean toward Democrats, but the margin between Dold and now-Rep. Brad Schneider in an upscale, lakeside district north of Chicago was only about 2,500 votes. Democrat Cheri Bustos, meanwhile, ousted Schilling by about 18,000 votes in a district that takes in the northwestern corner of the state.

At the same time, Democrats are gearing up to try to snatch away a district in the state’s midsection from first-term Republican Rodney Davis. Davis also faces a primary challenge, but former Miss America Erika Harold has not shown to be a serious threat.

New England

New England is the only region where one party is completely on offense with nothing to defend — Republicans lost their only House members in these six states in 2012, when New Hampshire Reps. Charles Bass and Frank Guinta were defeated.

Their best chance to establish a beachhead will probably be in New Hampshire, where Democratic Reps. Ann McLane Kuster and Carol Shea-Porter are both vulnerable. The two seats share a two-decade history of rising or falling together from one party to another.

Elsewhere in the region, Republicans are looking at individual races in Connecticut, Massachusetts and Maine. The latter two present unique opportunities.

Massachusetts Democrat John F. Tierney eked out a win in 2012 in his North Shore district despite ethical questions. The Republican hope is that Tierney will lose this time without popular Democratic Sen. Elizabeth Warren above him on the ballot.

And Maine, a politically quirky state with an occasional Republican impulse, will feature an open-seat race in the vast northern district to replace Democrat Michael H. Michaud, who is running for governor.

South

For now, the South is all about two conservative Democrats in hostile territory and a mix of Florida races.

John Barrow of southeastern Georgia and Mike McIntyre of southeastern North Carolina are a pair of old-style Blue Dog Democrats who just refuse to lose. They are included in Walden’s “Slippery Seven.”

As for Florida, Democrats are hopeful that legal challenges to the state’s redistricting map will create more House opportunities, but Republicans brush off that notion.

Ethical questions continue to loom over Democrat Joe Garcia’s office — his chief of staff was fired and his communications director resigned in a reported absentee-ballot scandal — but he performed strongly in second-quarter fundraising. For now, House Democratic operatives maintain confidence that Garcia, who represents the southern tip of the state, is viable. Republicans do not, and they plan to attack him aggressively.

“I wouldn’t want to be Garcia right now,” a national Republican operative said. “It’s not going to be fun.”

Democrat Patrick Murphy also faces a tough re-election race in an East Coast district around Port St. Lucie and Jupiter. The Republican field is still coalescing, but in the meantime Murphy is racking up exceptionally strong fundraising numbers. The question for Republicans is how much money and interest the race will draw without the outsized personality of Allen West, the former Army officer defeated by Murphy in 2012.

In the Panhandle, Democrats landed a star recruit in Gwen Graham, daughter of former Sen. Bob Graham. While it’s still unclear if she will face a contested primary, national Democrats hope that she can bring down Republican incumbent Steve Southerland II.

Southwest

Like Illinois, Arizona emerged from the last round of redistricting as a central front in any House struggle. Three of the state’s nine seats are competitive, and Democrats swept the trio in 2012.

Democratic incumbent Ann Kirkpatrick, an ex-prosecutor, is uniquely appealing to Native Americans and rural voters in her Republican-leaning district, which sprawls across much of the northern and eastern parts of the state.

In a newly redrawn suburban Phoenix district, Republicans in 2012 unloaded years of opposition research on Democrat Kyrsten Sinema to no avail. She won, and now she has the advantages of incumbency and a reputation on the Hill as one of the hardest-working and politically savvy freshmen.

Then there is Democrat Ron Barber, the former aide to Rep. Gabrielle Giffords who was wounded with her during an attack in suburban Tucson in 2011. Democrats are deeply concerned about his prospects for keeping the seat, which he won after she stepped down. Then again, the district is always a concern, and Barber has a seasoned political team with a track record of finding a way to win. Barber faces a rematch against retired Air Force Col. Martha McSally.

Beyond Arizona, an exciting race is brewing in the eastern Denver suburbs. Republican Mike Coffman, who survived a dramatic redrawing of his district in 2012, will face off against former Democratic state House Speaker Andrew Romanoff.

And another rematch is brewing in a vast district in southwestern Texas between Democratic incumbent Pete Gallego and Republican former Rep. Francisco “Quico” Canseco.

West

Top GOP and Democratic strategists generally agree that Republican Gary G. Miller of California is the most endangered incumbent. He won re-election last year in his San Bernardino--based district thanks to California’s new nonpartisan “jungle” primary rules, under which the top two vote-getters, regardless of party, advance to a runoff. At this point, according to Rothenberg Report/CQ Roll Call ratings, Miller is the only incumbent who is an underdog in his own district.

Besides Miller’s, a handful of other California seats are in play. There are a number of endangered Democrats, but none more so than Scott Peters. Peters will face a top GOP recruit, ex-San Diego Councilman Carl DeMaio.

In Utah, one of the most difficult of the GOP’s seven prime targets, Democrat Jim Matheson, will face Sarasota Springs Mayor Mia Love in a central Utah district. Love is running a determined and revamped campaign against her old rival.

EMILY’s List-backed Erin Bilbray-Kohn announced in July her challenge to Republican incumbent Joe Heck in a Las Vegas-area district of Nevada.

“It’s going to be a fight, but Joe’s been down that road before,” a national Republican operative said.

Emily Cahn and Shira Toeplitz contributed to this report.A version of this article originally appeared in the Sept. 2 edition of CQ Weekly.